/Engine/Plugins/Experimental/GeometryScripting/Source/GeometryScriptingCore/Public/GeometryScript/MeshBasicEditFunctions.h
Control how details like mesh attributes are handled when one mesh is appended to another
[USTRUCT](Programming/UnrealArchitecture/Reference/Structs)([BlueprintType](Programming/UnrealArchitecture/Reference/Structs/Specifiers/BlueprintType)) struct FGeometryScriptAppendMeshOptions
EGeometryScript...
CombineMode
How attributes from each mesh are combined into the result.